One of the most frequently performed operations in a microbiology laboratory is a staining procedure, the Gram stain, which is used to broadly classify bacteria as either Gram-positive or Gram-negative. The Gram stain, normally, is a manual four-step operation in which a primary stain is applied to a bacterial smear on a slide, followed by a mordant, usually an iodine solution, a decolorizer and a counterstain. It would be highly desirable to automate this procedure in order to free the operator or lab technician for other work and to remove certain subjective evaluations such as the time required for colorization. Two known automated Gram stain machines have been developed and both units operate on a "batch" system where slides are automatically transported through troughs containing staining solutions. The obvious drawback to these prior art systems is the possibility of contamination, either through the staining solution themselves or by transfer from previously processed slides. This uncertainty as to the possible contamination has precluded wide acceptance of the batch system by most laboratories.
It is therefore an object of the present invention to provide a novel apparatus for automatically making individual single laboratory Gram-stains on bacteria-inoculated slides.
Another object of the present invention is an apparatus for making individual laboratory Gram-stains that minimizes human error as well as the possibility of contamination of the individual slides.
A further object of the present invention is an apparatus for automatically flooding an inoculated slide with increments of a primary stain, a mordant, a decolorizer, a counterstain and a wash solution in a sequential manner.
An additional object of the present invention is a method of making individual Gram stains in an automatic and sequential operation without extended handling by the lab technician.